7. Acid-Base Flashcards
What is an acid
a compound that DONATES ions.
What is a base?
a compound that will BIND to an H ion.
What is the normal pH range for blood?
7.35-7.45
What is acidosis?
when animals pH range is below the normal average. inc in acid or loss of base
What is alkalosis
when animals pH is above normal range. inc in base or loss of acid
What is buffering and how is it done?
The natural buffering systems of the body to maintain pH.
Chemical buffering - K & H ion exchange btw the IC and EC space
Ion excretion in urine - kidneys able to control excretion and retention of bicarb and H to alter pH
Adjustment of RR - adjusting RR, Co2 lvls in blood are altered which affects pH
What are the arterial parameters for pH, pCo, HCO, BE, and pO?
pH - 7.40
pCO - 40
HCO - 25
BE - 0
pO - 95
What are the venous blood parameters for pH, pCo, HCO, BE, pO
pH - 7.35
pCO - 45
HCO - 24
BE - 0
pO - 40
Why is pH important?
Changes in pH can affect enzyme and cell func - affect tissue and organ func including brain and heart - death
Presence of a change in body pH may also help us t determine the type of pathology that is occurring.
What is an example of chemical buffering?
inc EC H conc are what causes the pH of the animal to dec creating an acidosis. If some H shifts into cells, the pH of the animal will inc. This is achieved by exchanging IC K for EC H. The shift in K to EC space can lead to hyperkalemia (important to correct acidosis)
Describe the carbonic acid equilibrium
Cells prod CO as a by-product of cellular metabolism.
CO2 lvls will inc if gas exchange thru lungs is impaired. CO2 lvls will dec if animals RR is inc due to panting or hyperventilation
CO2 reacts w/ H20 to form carbonic acid (H2CO3). Carbonic acid not stable, breaks down to bicarb (HCO3) and H. Bicarb is base, H are acid
Describe what Metabolic acidosis is?
Blood pH is <7.3
- Loss of bicarb (as D)
- Gain of organic acids (ketoacids, uremic acids, lactic acids)
What is base excess?
BE is measure of metab acidosis - mmol/L or mEq/L
it is the amount of a strong acid that would be req to bring pH to 1L of blood to 7.4
BE inc w/ metab alkalosis and dec with metal acidosis
if value is zero (+/- 5), there is no metabolic acidosis.
When value for BE is <-5 is called base deficit
How do you treat metab acidosis?
mild to mod - pH 7.45-7.2
may rely of general therepay and correct underlying problems, fluids to improve tissue func,
allow odies to homeostatic mechanisms to correct pH
Mod to severe - pH <7.2
Generally corrected - direct benefits, may promote excretion of toxic acids
What is resp acidosis?
Low pH, caused by an accumulation of CO
high CO drives prod of carbonic acid
underlying causes - lung disease, too much anesthetic gas
Changes in pCO indicate ventilation problems
How do you treat resp acidosis?
anesthesia - check anesthetic depth, inc ventilation rate, reduce dead space
diseased lung - improve lung fun w/ bronchodilators, diuretics, antibiotics, anti inflam
Describe metab alkalosis + TX
pH exceeds 7.45
Caused by excess of bicarb + loss of H, may occur w/ V or upper GI obstruction
tx w/ aggressive fuid therapy w/ o.9% saline. IV fluids will dilute the bicard in blood. Extra Cl from the fluids will inc the excretion of bicarb in the urine
Describe resp alkalosis + Treatment
A pH of >7.45
Low pCO
Caused by hyperventilation - stress, anxiety, excessive manual ventilation during anesthesia
TX the underlying issue, manually ventilated RR rate should be decreased. remove stressors or give anti-anxiety meds
What are ways to tell pH imbalances and if there is compensation?
- look at pH - Within range?
- look at pCO - inc w/ resp acid, dec with resp alk
- Look at bicarb - inc with metab alk, dec with metab acid
- Compensation? is the bicarbs and CO vales corresponding w/ pH abnormality that we are seeing? If not, the patient is compensating
Blood gas Example - pH 7.55, pCO 23mmHg, HCO 25
(7.35-7.45) patient is alkalotic
(40mmHg) pCO is low (causes pH to inc as H prod is decreased = alkalosis)
(25mEq/L) normal, not contributing to change of pH in patient
Patient has resp alkalosis, HCO lvls not changed so patient not compensating
Blood gas Example - pH 7.28, pCO 20mmHg, HCO 20mEq/L
pH - Decreased = acidotic
pCO - Decreased = pH to inc cause H is dec
HCO - Low, cause pH to decrease
Bc low bicarb lvls and low pH = metab acidosis
Bc low pCO, respi compensation
